Information signal processing apparatus for detecting both dropout of information signals and absence thereof

Abstract

An information signal processing apparatus is arranged to detect an amplitude level of an input information signal with a first time constant and to obtain a first amplitude level detection signal which corresponds to the amplitude level of the input information signal detected; to detect an amplitude level of the input information signal with a second time constant which differs from the first time constant and to obtain a second amplitude level detection signal which corresponds to the amplitude level of the input information signal thus detected; to compare the first and second amplitude level detection signals with each other; and to detect any dropout of the input information signal according to the result of comparison.

What is claimed is:  
     
       1. An information signal processing apparatus for processing information signals, comprising: 
       a) amplitude level attenuating means arranged to receive an information signal to attenuate the level of amplitude of the information signal inputted and to output a resultant signal;  
       b) output means arranged to receive both the information signal amplitude attenuated by said amplitude level attenuating means and the information signal not amplitude attenuated and to output either the amplitude attenuated information signal or the information signal not amplitude attenuated;  
       c) first detecting means for outputting a first detection signal which corresponds to a first amplitude level of the information signal outputted from said output means;  
       d) second detecting means for outputting a second detection signal which corresponds to a second amplitude level of the information signal inputted to said amplitude level attenuating means;  
       e) dropout detecting means arranged to compare the first detection signal outputted from said first detecting means with the second detection signal outputted from said second detecting means and to detect, according to the result of the comparison, whether or not a dropout has taken place in the information signal inputted to said amplitude level attenuating means and said second detecting means; and  
       f) information signal input detecting means arranged to detect the presence or absence of the information signal inputted to said amplitude level attenuating means and said second detecting means according to whether or not the first detection signal has been outputted from said first detecting means.  
     
     
       2. An apparatus according to claim  1 , wherein said second detecting means is arranged to have a larger detection gain than said first detecting means. 
     
     
       3. An apparatus according to claim  1 , wherein said information signal includes a reproduced information signal reproduced from a recording medium. 
     
     
       4. An apparatus according to claim  1 , wherein said output means is arranged to output the information signal amplitude attenuated by said amplitude level attenuating means when said information signal input detecting means is detecting the presence or absence of the information signal inputted to said amplitude level attenuating means and said second detecting means and to output the information signal not amplitude attenuated by said amplitude level attenuating means when said dropout detecting means is detecting whether or not a dropout has taken place in the information signal inputted to said amplitude level attenuating means and to said second detecting means.